Loris Remy, Van Walle Ivo, De Greve Henri, Beeckmans Sonia, Deboeck Francine, Wyns Lode, Bouckaert Julie
Laboratorium voor Ultrastructuur, Instituut voor Moleculaire Biologie, Building E, Vrije Universiteit Brussel and Vlaams Instituut voor Biotechnologie, Pleinlaan 2, B-1050 Brussel, Belgium.
J Mol Biol. 2004 Jan 30;335(5):1227-40. doi: 10.1016/j.jmb.2003.11.043.
The crystal structure of a Man/Glc-specific lectin from the seeds of the bloodwood tree (Pterocarpus angolensis), a leguminous plant from central Africa, has been determined in complex with mannose and five manno-oligosaccharides. The lectin contains a classical mannose-specificity loop, but its metal-binding loop resembles that of lectins of unrelated specificity from Ulex europaeus and Maackia amurensis. As a consequence, the interactions with mannose in the primary binding site are conserved, but details of carbohydrate-binding outside the primary binding site differ from those seen in the equivalent carbohydrate complexes of concanavalin A. These observations explain the differences in their respective fine specificity profiles for oligomannoses. While Man(alpha1-3)Man and Man(alpha1-3)[Man(alpha1-6)]Man bind to PAL in low-energy conformations identical with that of ConA, Man(alpha1-6)Man is required to adopt a different conformation. Man(alpha1-2)Man can bind only in a single binding mode, in sharp contrast to ConA, which creates a higher affinity for this disaccharide by allowing two binding modes.
来自非洲中部豆科植物血木树（Pterocarpus angolensis）种子的一种甘露糖/葡萄糖特异性凝集素的晶体结构已通过与甘露糖和五种甘露寡糖形成复合物而确定。该凝集素含有一个典型的甘露糖特异性环，但其金属结合环类似于来自欧洲荆豆（Ulex europaeus）和紫穗槐（Maackia amurensis）的具有不相关特异性的凝集素的金属结合环。因此，在主要结合位点与甘露糖的相互作用是保守的，但主要结合位点之外的碳水化合物结合细节与伴刀豆球蛋白A（ConA）的等效碳水化合物复合物中观察到的不同。这些观察结果解释了它们各自对寡甘露糖的精细特异性谱的差异。虽然Man(α1-3)Man和Man(α1-3)[Man(α1-6)]Man以与ConA相同的低能构象与PAL结合，但Man(α1-6)Man需要采用不同的构象。Man(α1-2)Man只能以单一结合模式结合，这与ConA形成鲜明对比，ConA通过允许两种结合模式对这种二糖产生更高的亲和力。
